The centre of mass of a system of three particles of masses 1g , 2g and 3g is taken as the origin of a coordinate system. The position vector of a fourth ….

Q: The centre of mass of a system of three particles of masses 1 g , 2 g and 3 g is taken as the origin of a coordinate system. The position vector of a fourth particle of mass 4 g such that the centre of mass of the four particle system lies at the point (1 , 2 , 3) is α (i + 2j + 3k ), where α is a constant. The value of α is

(a) 10 / 3

(b) 5 / 2

(c) 1 / 2

(d) 2 / 5